Fix for llvm-dis/llvm-bcanalyzer overflows

Summary:
These tools failed for a very large bitcode file produced by LTO due to
64-bit values being assigned to 32-bit types. For the BitstreamReader.h
fix, the value initially fit into the 32-bit unsigned, but there was an
overflow when multiplying by 32 furter below to compute the bit offset.

No test case in the patch as this requires a huge bitcode file.

Reviewers: pcc, george.karpenkov

Subscribers: mehdi_amini, a.sidorin, llvm-commits

Differential Revision: https://reviews.llvm.org/D47731

llvm-svn: 333942

include/llvm/Bitcode/BitstreamReader.h

@@ -429,7 +429,7 @@ public:
     // don't care what code widths are used inside of it.
     ReadVBR(bitc::CodeLenWidth);
     SkipToFourByteBoundary();
-    unsigned NumFourBytes = Read(bitc::BlockSizeWidth);
+    size_t NumFourBytes = Read(bitc::BlockSizeWidth);
 
     // Check that the block wasn't partially defined, and that the offset isn't
     // bogus.

tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp

@@ -602,7 +602,7 @@ static bool ParseBlock(BitstreamCursor &Stream, BitstreamBlockInfo &BlockInfo,
     ++BlockStats.NumRecords;
 
     StringRef Blob;
-    unsigned CurrentRecordPos = Stream.GetCurrentBitNo();
+    uint64_t CurrentRecordPos = Stream.GetCurrentBitNo();
     unsigned Code = Stream.readRecord(Entry.ID, Record, &Blob);
 
     // Increment the # occurrences of this code.